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"Caffeine"
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Caffeine-Induced Ca.sup.2+ Oscillations in Type I Horizontal Cells of the Carp Retina and the Contribution of the Store-Operated Ca.sup.2+ Entry Pathway
The mechanisms of release, depletion, and refilling of endoplasmic reticulum (ER) Ca.sup.2+ were investigated in type I horizontal cells of the carp retina using a fluo-3-based Ca.sup.2+ imaging technique. Exogenous application of caffeine, a ryanodine receptor agonist, induced oscillatory intracellular free Ca.sup.2+ concentration ([Ca.sup.2+ ].sub.i) responses in a duration- and concentration-dependent manner. In Ca.sup.2+ -free Ringer's solution, [Ca.sup.2+ ].sub.i transients could also be induced by a brief caffeine application, whereas subsequent caffeine application induced no [Ca.sup.2+ ].sub.i increase, which implied that extracellular Ca.sup.2+ was required for ER refilling, confirming the necessity of a Ca.sup.2+ influx pathway for ER refilling. Depletion of ER Ca.sup.2+ by thapsigargin triggered a Ca.sup.2+ influx which could be blocked by the store-operated channel inhibitor 2-APB, which proved the existence of the store-operated Ca.sup.2+ entry pathway. Taken together, these results suggested that after being depleted by caffeine, the ER was replenished by Ca.sup.2+ influx via store-operated channels. These results reveal the fine modulation of ER Ca.sup.2+ signaling, and the activation of the store-operated Ca.sup.2+ entry pathway guarantees the replenishment of the ER so that the cell can be ready for response to the subsequent stimulus.
Journal Article
Effects of Different Caffeine Dosages on Maximal Physical Performance and Potential Side Effects in Low-Consumer Female Athletes: Morning vs. Evening Administration
While previous studies have explored a range of factors governing the optimal use of caffeine (CAF) in athletes, limited research has explored how time of day (TOD) affects the ergogenic effects of various CAF dosages on physical performance. This study aimed to increase knowledge about how different recommended CAF doses (3 mg/kg vs. 6 mg/kg) ingested at different TODs affected maximal high-intensity physical performance and the perception of potential side effects in female athletes. In this double-blind, randomized, and counterbalanced study, 15 low CAF consumer athletes (aged 18.3 ± 0.5 y) underwent six trials, including three testing conditions assessed across two TODs: one in the morning (08:00 a.m.) and one in the evening (06:00 p.m.). During each condition, the participants ingested either a placebo, 3 mg/kg CAF (CAF (3 mg)), or 6 mg/kg CAF (CAF (6 mg)) capsules 60 min before each test with an in-between washout period of at least 72 h. In each trial, the participants performed a countermovement jumps test (CMJ), a modified agility t test (MATT), a repeated sprint ability (RSA), a rating of perceived exertion (RPE), and finally, a CAF side effects questionnaire. Our findings indicate the absence of an ergogenic effect on CMJ, MAT, and RSA performance in the evening after administering CAF (3 mg) or CAF (6 mg) compared to a placebo. Likewise, when CAF was ingested in the morning, there was an improvement in these performances with both CAF (3 mg) and CAF (6 mg), with greater improvement observed after CAF (6 mg). Additionally, neither the CAF dosage nor the TOD had a significant effect on the RPE. The occurrence of side effects increased significantly after the evening ingestion of CAF, particularly with a moderate dose of CAF (6 mg). Our findings indicate that the effectiveness of CAF depends on the TOD and CAF dosage. When ingested in the morning, a moderate dose of CAF (6 mg), rather than CAF (3 mg), is more effective in improving short-term physical performance without affecting CAF side effects in female athletes. Nevertheless, when ingested in the evening, neither dose was sufficient to enhance short-term physical performance, and both dosages increased the incidence of CAF side effects, particularly at a moderate dose.
Journal Article
The effects of caffeine mouth rinsing on selective attention as a function of different caffeine concentrations and perceived taste intensity in recreationally active males at rest: a randomized placebo-controlled cross-over trial
Rationale
The effect of caffeine mouth rinsing (CAF-MR) on cognitive performance has not been thoroughly investigated.
Objectives
To evaluate the effects of different concentrations of CAF-MR on selective attention in relation to perceived taste intensity.
Methods
A total of 30 healthy and recreationally active male subjects were included in this randomized, double-blind, placebo-controlled crossover trial. Interventions included MR
for 20 s at rest
with three different caffeine solutions (0.24% [60 mg/
25 mL
], 0.6% [150 mg/
25 mL
], and 1.2% [300 mg/25 mL]), MR with 25 mL water (placebo), and no MR (control). Data on Victoria Stroop Test (VST) and the perceived taste intensity were recorded at five sessions.
Results
CAF-MR-300 mg intervention significantly decreased completion time (from 62.93 ± 19.07 to 57.01 ± 16.74 s,
p
= 0.002 in Part D), while CAF-MR-150 mg intervention significantly decreased number of errors in Part D (7.00 ± 6.21 vs. 5.63 ± 5.76,
p
= 0.04) and Part C (
8.77
± 8.80 vs. 7.10 ± 7.11,
p
= 0.02). Perceived difficulty was significantly decreased both after CAF-MR with 150 mg (5.57 ± 1.65 vs. 4.77 ± 1.98,
p
= 0.006) and 300 mg (5.95 ± 1.77vs. 4.67 ± 1.96,
p
< 0.001). Perceived taste intensity for 300 mg of caffeine was negatively correlated with completion time (r: ranged, 0.37 to 0.46, p ranged, 0.045 to 0.009) after 300 mg, 150 mg (p ranged, 0.04 to 0.005) and placebo (p ranged 0.044 to 0.03) interventions.
Conclusions
This study is the first to demonstrate that CAF-MR shows dose-dependent effects on selective attention in healthy recreational males, such as improved speed (for 300 mg caffeine), reduced error rate (for 150 mg caffeine) and decrease in perceived difficulty (for 150 and 300 mg caffeine).
Journal Article
Caffeinated chewing gum produces comparable strength and power gains to capsules with fewer side effects in resistance-trained men
Caffeine, widely used as an ergogenic aid, has been extensively studied regarding its dosage and timing of ingestion. However, the impact of different administration methods on caffeine's performance-enhancing effects remains relatively underexplored. This study compared the effects of caffeine administered via chewing gum versus capsules on maximal strength, muscular power, and side effects during bench press and back squat exercises.
Sixteen resistance-trained males participated in a double-blind, randomized trial, ingesting either a 4 mg/kg caffeine capsule (CC) or placebo capsule (PC) one hour before testing, or a 4 mg/kg caffeinated gum (CG) (4 mg/kg) or placebo gum (PG) five minutes prior. Assessments including one-repetition maximum (1RM) and muscular power at 25%, 50%, 75%, and 90%1RM for bench press and back squat.
Caffeine increased 1RM (+2.1-5.0%) and muscular power (+6.1-20.0%) in both the bench press and back squat compared to placebo (all
< 0.05). However, no significant differences were observed between CC and CG for maximal strength or muscular power (all
> 0.05). Furthermore, CG was associated with fewer reports of gastrointestinal discomfort (12.5% vs. 37.5%) immediately post-exercise and tachycardia/heart palpitations (0% vs. 25.0%) at 24 hours compared to CC (all
< 0.05).
Caffeinated gum (4 mg/kg) produced ergogenic effects comparable to capsules in enhancing maximal strength and muscular power during bench press and back squat exercises, with fewer side effects in resistance-trained men.
Journal Article
Caffeine as a Factor Influencing the Functioning of the Human Body—Friend or Foe?
Nowadays, caffeine is one of the most commonly consumed substances, which presents in many plants and products. It has both positive and negative effects on the human body, and its activity concerns a variety of systems including the central nervous system, immune system, digestive system, respiratory system, urinary tract, etc. These effects are dependent on quantity, the type of product in which caffeine is contained, and also on the individual differences among people (sex, age, diet etc.). The main aim of this review was to collect, present, and analyze the available information including the latest discoveries on the impact of caffeine on human health and the functioning of human body systems, taking into account the role of caffeine in individual disease entities. We present both the positive and negative sides of caffeine consumption and the healing properties of this purine alkaloid in diseases such as asthma, Parkinson’s disease, and others, not forgetting about the negative effects of excess caffeine (e.g., in people with hypertension, children, adolescents, and the elderly). In summary, we can conclude, however, that caffeine has a multi-directional influence on various organs of the human body, and because of its anti-oxidative properties, it was, and still is, an interesting topic for research studies including those aimed at developing new therapeutic strategies.
Journal Article
